1. Field of the Invention
The present invention relates to an inkjet recording apparatus and an inkjet recording method, and more particularly, to an inkjet recording apparatus and an inkjet recording method whereby a recording medium can be conveyed by vacuum suction conveyance without creating suction marks in the recording medium.
2. Description of the Related Art
An inkjet recording apparatus which carries out recording by depositing ink droplets onto the recording surface of a recording medium is widely used in general applications as an image recording apparatus or an image forming apparatus, such as a printer, a facsimile device, a copying machine, or the like. In an inkjet recording method which uses a water-based ink, since ink droplets are ejected and deposited onto the recording medium, then a phenomenon known as cockling (a swelling deformation of the recording medium due to absorption in the recording medium) occurs due to the water content of the ink bleeding into the recording medium, such as paper, and the recording quality is lowered by this phenomenon.
In particular, in the case of a system which carries out high-speed printing in a single pass using a fixed long head having a high-density arrangement, it is necessary to provide a device for conveying the recording medium reliably with high accuracy compared to the related art, because the floating up of the recording medium itself, and the like, affects recording. It is also necessary to suppress cockling of the recording medium after printing and to improve the drying performance when operating at high speed.
In view of problems of this kind, for example, Japanese Patent Application Publication No. 2008-179012 discloses an apparatus comprising a device which dries a recording medium while conveying the recording medium by suction on a rotating drum, in order to dry the ink on the recording medium after printing reliably in a short time. Furthermore, Japanese Patent Application Publication No. 2009-35010 discloses an apparatus comprising a suctioning unit having a plurality of suction holes provided in the direction of conveyance of the recording medium, the suction holes being closed when no recording medium is conveyed, and the suction holes being successively opened in accordance with the leading end of a recording medium when the recording medium is conveyed. Consequently, when a recording medium which has been recorded is conveyed, it is possible to open only the suction holes in the portion where the leading end of the medium is situated, and therefore it is possible to concentrate the suctioning performance of the fan in the suction holes which are open, and in particular, it is possible to suction reliably the leading end of the recording medium which has strong curl.
Furthermore, Japanese Patent Application Publication No. 2004-216652 discloses an apparatus in which an air flow channel member 14 in which two air flow channels a and b are formed is disposed between a printing platform in which a plurality of suction holes are formed and two suction fans A, B, and the two suction fans A, B and the two air flow channels a, b correspond respectively to two paper conveyance flow channels I, II which are composed in parallel. When printing is carried out only in respect of the paper conveyance flow channel I of the paper conveyance flow channels I and II, the suction fan B corresponding to the paper conveyance flow channel II where printing is not carried out is not driven, whereas only the suction fan A corresponding to the paper conveyance flow channel I where printing is carried out is driven. Japanese Patent Application Publication No. 2000-153604 discloses providing a suction area changing device which changes the effective suction area where a recording material can be suctioned and caused to adhere to a platen having a plurality of suction holes, and a shielding body which shields the suction holes of the platen is disposed movably to act as this changing device, whereby the recording material can be suctioned and caused to adhere stably to the surface of the platen, even if the breadthways dimension of the material in the direction perpendicular to the conveyance direction varies.
However, in the apparatus described in Japanese Patent Application Publication No. 2008-179012, the cellulose bonds in the image portion of the recording medium directly after recording are severed by the water content in the ink, and the image is in a state of reduced rigidity. If the medium is suctioned in this state, then the portions of the image area where the suction holes are disposed become depressed, and since the image area is dried in this state, then the depressions in the suction hole portions remain as suction marks after recording, thus leading to a problem of impaired image quality. Furthermore, if the medium is dried on a conveyance body having a heated surface in order to keep the distance between the inkjet head and the recording medium uniform, and to prevent the recording medium from contacting the head, a prescribed suction time or greater is required in order to promote the heating of the rear surface, but there is a trade-off in that the longer the suction time, the more liable suction marks are to occur in the medium. Moreover, Japanese Patent Application Publication No. 2009-35010 does not recognize the problems relating to depressions (suction marks) which are created by the suction holes, and suction marks have been especially liable to occur in the leading end portion of the recording medium which is suctioned first.
Furthermore, Japanese Patent Application Publication No. 2004-216652 and Japanese Patent Application Publication No. 2000-153604 only describe disabling the operation of the suction mechanism in a non-suctioned region, and make no mention of switching the suction region (recording region).